无机非金属材料工程专业英语 第7章.ppt

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1、Chapter7DeformationandstrengtheningmechanismsWhystudydeformationandstrengtheningmechanism?Mostofmetallicproductsareproducedthroughdeformingthemetalsomehowtoobtaindesiredshape,sizeandstrength.Butwhatfactorswouldinfluencetheprocessofdeformation?Youmayhaveanexperiencethatanironwire

2、willgettougheranditwillbreakfinallywhenitisbendedfortimes.Doyouknowwhy?Studyondeformationandstrengtheningmechanismwillhelpususeanddevelopmaterialsbetter.Whatshouldyoubeabletodoafterstudyingthischapter?Describedislocationmotionfromanatom’sperspective.Understandtherelationshipsbet

3、weendislocationmotionandplasticdeformationofmetallicmaterials.Defineslipsystemandexplaintheinfluenceofslipsystemonthedeformabilityofmaterials.Explainmechanismofgrainboundarystrengthening,solid-solutionstrengthening,strainhardening.Describerecoveryandrecrystllizationintermsofboth

4、thealternationofmicrostructureandmechanicalcharacteristicsofthematerial.Importanttermsandconcepts:Coldworking冷加工Criticalresolvedshearstress临界分剪切应力Dislocationdensity位错密度Graingrowth晶粒生长Latticestrain晶格应变Recovery回复Recrystallizationtemperature再结晶温度Resolvedshearstress分剪切应力Slip滑移Slipsy

5、stem滑移系Recrystallization再结晶solid-solutionstrengthening固溶强化strainhardening应变强化strengtheningbygrainsizereduction细晶强化annealing退火temper回火quench淬火ageing时效naturalageing自然时效artificalageing人工时效dislocationmultiplication位错繁殖misorientation位相差异equiaxedgrains等轴晶粒elongatedgrains拉长晶粒strainfiel

6、d应变场Stressfield应力场Keyknowledgepoints:Deformationsmechanismsformetals1.Historical:1930s,theoryandactuallymeasureddiscrepancyinmechanicalstrengths1950s,dislocationbeexaminedbyelectronmicroscope2.BasicconceptsofdislocationsPlasticdeformationcorrespondstothemotionoflargenumbersofdis

7、locations.Anedgedislocationmovesinresponsetoashearstressappliedinadirectionperpendiculartoitsline.Inanedgedislocation,localizedlatticedistortionexistsalongtheendofanextrahalf-planeofatoms.ThemechanicsofdislocationmotionarerepresentedinFig.7.1ThemechanicsofdislocationmotionFig.7.

8、1Atomicrearrangementsthataccompanythemotionofan